Slip ring spacer for insulated conduit systems



B. E. EATON March 31, 1964 SLIP RING SPACER FOR INSULATED CONDUITSYSTEMS Filed March 5, 1962 uvmvrom ATTORNEYS. I

United States Patent 3,126,918 SLIP RING SPACER FOR TNSULATED CONDUITSYSTEMS Burton E. Eaton, Deerfield, 111., assignor to Midwesco, Inc., acorporation of lliinois Filed Mar. 5, 1962, Ser. No. 177,675 5 Claims.((31. 138-113) This invention relates to conduit and, more particularly,to conduit for connecting hot or cold fluids such as steam orrefrigerant mixtures, such conduit comprising an insulated inner pipeabout which is disposed an outer conduit casing, and means for uniformlyspacing the insulated inner pipe from the outer casing.

Heretofore, conduit of the type described has been constructed such thatthe inner pipe was spaced from the outer casing by spacer members whichwere rigidly secured to the inner pipe. The construction resulted inundesirable heat exchange between the inner pipe and the outer casing.Further, as a result of rigidly securing the spacer members or supportsto the inner pipe, as the inner pipe expanded and contracted there waswearing movement between the supports and the inner wall of the outercasing, eventual-1y resulting in the effecting of an opening or breakWall of the outer casing. While the use of rollers to overcome the wearproblem between the inner pipe and the outer casing has been proposed,such construction is not altogether successful from the standpoint ofcost and maintenance.

Previous supports or spacer members between the inner pipe and the outercasing provided only one or two points of contact between the spacermember and outer casing, resulting in undesirably high shear loadingsbeyond acceptable design values and occasionally causing the support topunch through the wall of the outer casing. In addition, previoussupports often unduly restricted the proper air fiow and drainage in thespace between the inner pipe and outer casing.

An object of the present invention is to provide a conduit wherein thedeficiencies and disadvantages of prior constructions are obviated.

Another object of the present invention is to provide a conduitcomprising an inner pipe and an outer casing uniformly spaced therefromby novel support and spacer means which permit the inner pipe to beinsulated substantially continuously along its entire length.

Still another object of the present invention is to provide a conduitcomprising an inner pipe and a protective casing thereabout with spacingmeans between the inner pipe and the outer casing constructed andarranged to obviate wearing movement between the spacing means and theouter casing.

Yet another object of this invention is to provide a prefabricatedconduit comprising an insulated inner pipe disposed within an outercasing and provided with annular support members, of corrugated or nodalsheet metal, disposed between the inner pipe and outer casing touniformly space the inner pipe from the outer casing and to permitsubstantially unrestricted air movement and drainage in the annularspace between the inner pipe and the outer casing.

These and other objects of the present invention will become moreapparent hereinafter.

Broadly stated, this invention relates to a conduit comprising anelongated inner pipe for carrying a fluid, substantially continuousannular insulation surrounding said inner pipe, a plurality of sheetmetal lagging pieces on the insulation and having substantially nomovement relative thereto, an elongated outer casing disposed about andsurrounding the inner pipe, and spacer means for spacing the inner pipefrom the outer casing comprising a sup- 3,126,913 Patented Mar. 31, 1964port ring formed from nodalor corrugated sheet metal, the support ringbeing disposed between the lagging piece and the outer casing, thelagging pieces being slidable within and relative to the nodal supportring in response to expansion and contraction of the inner pipe, theinsulation electrically and thermally isolating the inner pipe from theouter casing.

The invention will be better understood from the following descriptionof a presently preferred embodiment of the invention, which isillustrated in the accompanying drawings wherein like parts areidentified by like reference numerals in each of the views and wherein:

FIG. 1 is a fragmentary sectional view illustrating a conduit embodyingthe present invention;

FIG. 2 is a perspective view on an enlarged scale illustrating thespacing means of the present invention;

FIG. 3 is an enlarged cross-sectional view taken along the line 3-3 ofFIG. 1; and

FIG. 4 is an enlarged sectional view illustrating a portion of a conduitembodying the present invention.

Referring to FIG. 1, there is illustrated a preferred embodiment of thepresent invention. The conduit, generally indicated at It is adapted tobe positioned in a trench in the ground and comprises an outer conduit,or casing, 11 and an inner conduit, or pipe, 12 disposed substantiallycoaxially therein. Provided about the inner pipe 12 is suitableinsulation 14, which may be formed from annular mats of fiber glass,asbestos, calcium silicate or the like. At'fixed about the insulation 14as spaced locations are liners or lagging pieces 16.

Disposed between the lagging pieces 16 and the inner wall of the outercasing 11 are spacer means 18 for substantially uniformly spacing theinner pipe from the outer casing,

As is more clearly seen in FIGS. 2 and 3, each lagging piece 16comprises a generally circular piece of sheet metal which is drawn upand tightly clamped to the insulation. Beneath the lagging pieces, theinsulation may be formed from semicylindrical members 14a and 14b. Theoverlapping ends of the lagging piece may then be suitably connected,as, for example, by spot welding.

The spacing means 18 are formed from an annulus of sheet metal that hasbeen preformed with nodes, of corrugations 19. The annular arrangementprovides that the outermost ridges of corrugations 19' are adapted toengage the outer casing 11 while the innermost ridges engage laggingpiece 16 at circumferentially spaced lines. It is apparent from FIG. 2that in the preferred embodiment of the invention the corrugationsextend longitudinally parallel to the axis of the inner pipe and outercasing. However, it is within the scope of the present invention andwill be apparent to one skilled in the art that the corrugations may beformed helically and thus extend at an angle to the longitudinal axis ofthe inner pipe.

Secured to the lagging piece 16 on opposite sides of the annular spacerring 18 and spaced axially from the edges of ring 18 are a pair ofarrestors or stop members 21. These stop members assure that inoperation each lagging piece 16 will always be located within itsassociated support ring 18.

The conduit illustrated in FIG. I normally will be constructed orprefabricated in sections in a factory or shop. When installed in thefield it is intended that the usual anchors and expansion joints will beprovided. Adjacent sections will be joined together, as in the past,with circumferential Welds of the inner pipe 12 and outer casing 11. Theinner pipe 12 normally is not assembled complete with insulation, so asto permit access in the field for effecting the circumferential buttweld 12a between adjacent pipe sections. Then, the semicylindricalinsulation sections 14a and 1411, cut to the precise axial length togive complete insulation of pipe 12, are applied. The sheet metallagging piece 16 may be applied around insulation sections 14a and 14b,thereby holding those sections assembled. Then the sheet metal spacerit; is assembled on lagging piece 16 and the entire assembly is slidinto a casing section 11.

:In use, upon the first passage of fluid through the inner pipe, theinner pipe will expand or contract. The lagging pieces 16, which areclamped onto and thereby fixed relative to the insulation, will alsomove. When either stop member 20 or 21 abuts the end of annular spacerring 18, the ring will be moved within the outer casing 11 to its finalposition. In subsequent operation each lagging piece 16 will sliderelative to and Within its associated ring 18. Thus, it is apparent thatafter the first heat-up of the system there is no wearing movementbetween spacer ring 18 and the outer casing 11. Since the inner pipe isspaced from spacer ring 18, there is no sliding wear on the inner pipe.As a consequence, the operating life of both the inner pipe and of theouter casing is increased.

By virtue of the corrugations 19 defining the annular spacer ring 18,the inner pipe 12 is substantially uniformly spaced from the inner wallof the outer casing.

It is apparent from FIGS. 3 and 4 that there are a relatively largeplurality of contact points (axial lines) between the lagging piece 16and the spacer ring 18, and between the ring 18 and the outer casing 11,as provided by the corrugations 19 of the ring 1-8. In a presentlypreferred embodiment of my invention, there are at least three lines ofcontact between the lagging piece 16 and spacer ring 1 8 and between thespacer ring 18 and the outer casing 11. The existence of a large numberof points of contact eifects a distribution of the spear loading on thecasing 11, thereby reducing possibility of punching a hole in the casing11, as when previous spacers provided only one or two points of contactwhich developed very high shear loadings. Thus, the possibility of thespacing means punching through the wall of the outer casing 11, whichhas occurred in previous designs, is virtually obviated for theindividual ring corrugations are yieldable and all deflection takesplace within the ring 18. Further, by virtue of the construction'ofsupport ring 18, maximum utilization is made of the annular spacebetween the insulation 14 surrounding the inner pipe 12 and the innerwall of outer casing 11 to provide increased space for air movement andfor drainage, inasmuch as approximately 95 percent of the annular spaceis unrestricted. The passages defined between the corrugations 19 andthe lagging pieces 16 and between the corrugations 19 and the supportring 18 are uniformly defined about the annular space such that air flowand drainage are substantially unrestricted in any radial position ofthe conduit. Thus in field installation, the straight sections ofconduit may be installed in any radial position.

It will be apparent that changes can be made in the construction andarrangement of the parts while accomplishing the objects and fallingwithin the scope of the invention. The inner pipe may be made from blackpipe, galvanized pipe, or wrought iron pipe, depending upon the use andfluid (liquid or gas) to be conducted within the inner pipe. In onepresently preferred form of the invention, the outer casing is spiralwelded steel made of 8, or 14 gauge black steel. Other suitable materialwill be apparent to those having ordinary skill in the art.

The insulation may be formed from a tube or cylinders of insulatingmaterial slipped over the inner pipe, irom contiguous annular segments,or from half-cylinders suitably interconnected. The latter arrangementis preferred where adjacent conduits have to be welded together in thefield. After welding, half-cylinders of insulation may be installedabout the joint. Then the lagging piece is affixed about the splitinsulation and the overlapping ends thereof are secured together. Ineach usage, the inner pipe is thermally and electrically isolated fromthe outer i casing substantially along its length. The spacers areconstructed to allow drainage and free flow of air within the annularspace between the inner pipe and outer casing and will permit theexpansion and contraction of the inner pipe without damage to theinsulation.

While there has been shown and described a particular embodiment of thisinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made therein without departing from theinvention and, therefore, it is intended in the appended claims to coverall such changes and modifications as fall within the true spirit andscope of the invention.

What I claim as new, and desire to secure by Letters Patent of theUnited States is:

1. Improved spacer means for conduits of the type having an inner pipefor carrying a fluid and an outer casing through which said inner pipeextends in spaced relation with the outer casing; said spacer meansincluding a ringlike axially elongated sheet metal lagging pieceoperatively secured to the inner pipe so as to move axially with theinner pipe in response to expansion or contraction of the inner pipe,and a sheet metal nodal-type spacer ring slidably arranged on saidlagging piece and adapted to engage the inner surface of an outer casingto space the inner pipe from the outer casing, whereby the inner pipeand the lagging piece operatively secured thereto are slidable withinthe spacer ring when the inner pipe extends or contracts.

2. Improved spacer means as in claim 1 wherein the axial length of thering-like lagging piece is greater than the 'axial length of the spacerring, to atford relative sliding movement of the lagging piece withinthe spacer ring.

3. Improved spacer means as in claim 2. including a stop element on thelagging piece adjacent an end thereof positioned to engage and move thespacer ring with the lagging piece, in the event the expansion orcontraction of the inner pipe would tend to move the end of the laggingpiece wholly or partly through the spacer ring.

4. A conduit comprising an elongated inner pipe for carrying a fluid,substantially continuous annular insulation surrounding said inner pipe,an elongated outer casing disposed about and surrounding said inner pipeand its insulation, and a plurality of axially spaced spacer means forspacing the inner pipe from the outer casing, each spacer meanscomprising a sheet metal annular lagging piece secured to theinsulation, a nodal-type annular spacer ring of sheet metal of lesserwidth than the width of a lagging piece disposed between the laggingpiece and the outer casing to providea plurality of axially extendinglines of support, said lagging pieces being slidable within and relativeto said spacer rings in response to expansion and contraction of theinner pipe, said insulation electrically and thermally isolating saidinner pipe from the outer casing, and stop members secured to eachlagging piece on opposite sides of said nodal-type spacer ring to assurethat the spacing between adjacent spacer rings will be maintained 'inuse.

5. In combination with a conduit casing and an insulated inner pipe inand disposed longitudinally thereof, lagging pieces afiixed to saidinsulated inner pipe at spaced locations and movable therewith inresponse to expansion and contraction of the inner pipe, and corrugatedsupport members disposed between the lagging pieces and the outer casingto provide a plurality of lines of support for spacing the inner pipefrom the outer casing, said lagging pieces being slidable within andwith respect to said support members in response to expansion andcontraction of the inner pipe, and including stop members on eachlagging piece disposed on opposite sides of an associated supportmember.

References Elitcrl in the file of this patent UNITED STATES PATENTS2,903,017 Cotman Sept. 8, 1959 2,914,090 Isenberg Nov. 24, 19592,938,569 Goodrich May 31, 1960

1. IMPROVED SPACER MEANS FOR CONDUITS OF THE TYPE HAVING AN INNER PIPEFOR CARRYING A FLUID AND AN OUTER CASING THROUGH WHICH SAID INNER PIPEEXTENDS IN SPACED RELATION WITH THE OUTER CASING; SAID SPACER MEANSINCLUDING A RINGLIKE AXIALLY ELONGATED SHEET METAL LAGGING PIECEOPERATIVELY SECURED TO THE INNER PIPE SO AS TO MOVE AXIALLY WITH THEINNER PIPE IN RESPONSE TO EXPANSION OR CONTRACTION OF THE INNER PIPE,AND A SHEET METAL NODAL-TYPE SPACER RING SLIDABLY ARRANGED ON SAIDLAGGING PIECE AND ADAPTED TO ENGAGE THE INNER SURFACE OF AN OUTER CASINGTO SPACE THE INNER PIPE FROM THE OUTER CASING, WHEREBY THE INNER PIPEAND THE LAGGING PIECE OPERATIVELY SECURED THERETO ARE SLIDABLE WITHINTHE SPACER RING WHEN THE INNER PIPE EXTENDS OR CONTRACTS.